/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package javax.el;

/**
 *
 */
public abstract class ValueExpression extends Expression {

	private static final long serialVersionUID = 8577809572381654673L;

	public abstract Class<?> getExpectedType();

	/**
	 * @param context The EL context for this evaluation
	 * @return The type of the result of this value expression
	 * @throws NullPointerException      If the supplied context is <code>null</code>
	 * @throws PropertyNotFoundException If a property/variable resolution failed because no match
	 *                                   was found or a match was found but was not readable
	 * @throws ELException               Wraps any exception throw whilst resolving a property or
	 *                                   variable
	 */
	public abstract Class<?> getType(ELContext context) throws NullPointerException, PropertyNotFoundException, ELException;

	/**
	 * @param context The EL context for this evaluation
	 * @return <code>true</code> if this expression is read only otherwise
	 * <code>false</code>
	 * @throws NullPointerException      If the supplied context is <code>null</code>
	 * @throws PropertyNotFoundException If a property/variable resolution failed because no match
	 *                                   was found or a match was found but was not readable
	 * @throws ELException               Wraps any exception throw whilst resolving a property or
	 *                                   variable
	 */
	public abstract boolean isReadOnly(ELContext context) throws NullPointerException, PropertyNotFoundException, ELException;

	/**
	 * @param context The EL context for this evaluation
	 * @param value   The value to set the property to which this value
	 *                expression refers
	 * @throws NullPointerException         If the supplied context is <code>null</code>
	 * @throws PropertyNotFoundException    If a property/variable resolution failed because no match
	 *                                      was found
	 * @throws PropertyNotWritableException If a property/variable resolution failed because a match was
	 *                                      found but was not writable
	 * @throws ELException                  Wraps any exception throw whilst resolving a property or
	 *                                      variable
	 */
	public abstract void setValue(ELContext context, Object value) throws NullPointerException, PropertyNotFoundException, PropertyNotWritableException, ELException;

	/**
	 * @param context The EL context for this evaluation
	 * @return The result of evaluating this value expression
	 * @throws NullPointerException      If the supplied context is <code>null</code>
	 * @throws PropertyNotFoundException If a property/variable resolution failed because no match
	 *                                   was found or a match was found but was not readable
	 * @throws ELException               Wraps any exception throw whilst resolving a property or
	 *                                   variable
	 */
	public abstract Object getValue(ELContext context) throws NullPointerException, PropertyNotFoundException, ELException;

	/**
	 * @param context The EL context for this evaluation
	 * @return This default implementation always returns <code>null</code>
	 * @since EL 2.2
	 */
	public ValueReference getValueReference(@SuppressWarnings("unused") ELContext context) {
		// Expected to be over-ridden by implementation
		return null;
	}
}
